Most telephone service providers offer voice messaging services for their subscribers. These services allow a calling party to leave a voice message for a subscriber when a call to the subscriber is unanswered or the line is busy. Many voice messaging services allow a calling party to send a message to a subscriber by accessing the voice messaging system directly without first calling the subscriber's directory number. The messages are then retrieved at the subscriber's convenience by accessing the voice messaging system via a telephone. Communications between the subscriber and the voice messaging system is over existing telephone lines.
When a voice message is received by the voice messaging system, it communicates with the central office switch and instructs the switch to send stutter dial tone to the subscriber's line when the subscriber's phone goes off-hook. The stutter dial tone serves to notify the subscriber that there are new voice messages waiting. When the subscriber has retrieved all new voice messages, the voice messaging system again communicates with the central office switch and instructs the switch to now send normal dial tone.
A problem with current voice messaging services is that they require the subscriber to lift the telephone handset and listen to the dial tone in order to check for new messages. Many subscribers will prefer the "hands-off" indicator of a traditional answering machine having a simple visual message waiting indicator, such as a lamp, or an audible indicator, such as a repeated beep.
One solution to this problem is to install equipment at the subscriber location to take advantage of in-band signaling protocols that support suppressed ringing messaging, such as the Voiceband Data Transmission Interface protocol as defined in the standards publications TR-NWT-000030, "Voiceband Data Transmission Interface Generic Requirements," Issue 2, Bellcore, October 1992, and SR-TSV-002476, "CPE Compatibility Considerations for the Voiceband Data Transmission Interface," Issue 1, Bul. 1, Bellcore, September 1993. This protocol is used to support Type I and Type II Caller ID (CID) and Caller ID on Call Waiting (CIDCW) applications.
Another in-band signaling protocol in use is the Analog Display Services Interface (ADSI) protocol, as defined in standards publications SR-INS-002461, "Customer Premises Equipment Compatibility Considerations for the Analog Display Services Interface," Issue 1, Bul. 3, Bellcore, December 1993, and TR-NWT-001273, "Generic Requirements for an SPCS to Customer Premises Equipment Data Interface for Analog Display Services," Issue 1, Rev. 2, Bellcore, June 1995. This protocol is used to support Type III CID and CIDCW applications on ADSI-compatible CPE. In particular, these protocols support Message Waiting ON and Message Waiting OFF in-band suppressed ringing message signaling.
In order to take advantage of the Voiceband Data Transmission Interface or the ADSI protocols, the user must install new equipment. This could result in prohibitively high expenses to individual users and businesses. However, many businesses and users already own PC's.
Accordingly, it is an object of the present invention to provide a computer integrated telephony system that uses the computer's display, internal audio system, or an external interface in concert with a telephony protocol that supports in-band signaling to indicate to a subscriber that a voice message is waiting.